Influence of Positioning Error on X-Map Estimation

Transcription

1 FP7 ICT-SOCRATES Influence of Positioning Error on X-Map Estimation Michaela Neuland, TUBS

2 Outline Motivation X-map estimation approach Simulation scenario Comparison of different X-maps Position error modelling Conclusion and next steps 2/13

3 Motivation Drive/walk tests are used for radio network planning and optimisation today expensive cover only a limited part of the network capture only a snapshot in time use mobiles as probes for the service quality X-map estimation function continuously monitors the network estimates the spatial characteristics of the network, e.g., coverage or throughput connects the UE measurements to an estimated geographic position may use other sources of information, e.g. prediction data X-map is a geographic map with overlay performance information depending on the positioning accuracy the UE measurement accuracy the number of measurements taken 3/13

4 X-map estimation approach X-Map Estimation Prediction Data Propagation Model Propagation Model Calibration Bin Update X-map UE/RAN Measurement, Time, Position UE Location and Measurement Unit (LMU) RAN Measurement Unit (RMU) Measurement, Time, Location Data UE 1 UE n approach 1: approach 2: 4/13

5 X-maps based on approach 1 (x,y) (x,y) (x,y) (x,y) (x,y) RSRP RSRP RSRP RSRP RSRP (x,y) RSRP (x,y) RSRP (x,y) RSRP RSRP + very accurate - RSRP values only for those pixels which are covered by a UE 5/13

6 X-maps based on approach 2 (x,y) (x,y) (x,y) (x,y) (x,y) RSRP RSRP RSRP RSRP RSRP (x,y) RSRP (x,y) RSRP (x,y) RSRP RSRP diff building natural areas waterways streets railway corr corr corr corr corr + RSRP value for every pixel in the X-map - less accurate 6/13

7 Simulation scenario city area of 1.5 km x 1.5 km in Germany 20 mobile users traces derived with the help of SUMO network information available (site location, sector orientation, tilt) realistic path loss predictions at 2.6 GHz used for determining 30 strongest cells for each user position reference for determining accuracy of the X-maps satellite orbits for a specific day and time 7/13 Source: Google Earth 5.0

8 Comparison of different X-maps (real position) approach 1 approach 2 approach 1 approach 2 µ σ µ σ /13

9 Position Error Modelling For LTE, three different localisation methods are foreseen Assisted Global Positioning System (A-GPS) Observed Time Difference of Arrival (OTDOA) Enhanced cell ID positioning method Model for the minimum mean square position error based on the Cramér- Rao lower bound found in the literature* This model is based on the geometry of enodebs / satellites and the UE number of measured signals standard deviation of the measurement error * C. Fritsche and A. Klein, Cramér-Rao Lower Bounds for Hybrid Localization of Mobile Terminals, 5th Workshop on Positioning, Navigation and Communication (WPNC 08), March /13

10 Position error modelling 1200 GPS OTDOA OTDOA histogram number of visible satellites number of hearable enodebs number of hearable enodebs For OTDOA measurements from at least 3 enodebs are necessary To improve hearability special positioning reference signals (PRS) with frequency reuse of 6 low interference subframes modelled by excluding the 6 strongest cells from interference calculation 10/13

11 Position error modelling 1200 GPS 3000 OTDOA 2000 OTDOA6 histogram number of visible satellites number of hearable enodebs number of hearable enodebs cumulative distribution function GPS OTDOA position error in m GPS OTDOA6 GPS+OTDOA6 valid positions 77.1 % 66.4 % 90.6 % mean error 8.3 m 16.3 m 8.8 m standard deviation 6.7 m 31.4 m 6.7 m 11/13

12 Comparison of X-maps with different positioning methods GPS GPS+OTDOA6 OTDOA6 approach 1 approach 2 µ σ µ σ GPS GPS+OTDOA OTDOA /13

13 Conclusion and next steps Two approaches for creating X-maps have been introduced Influence of the positioning error on the accuracy of the X-maps has been analysed approach 1 strongly depends on the accuracy of the positioning method approach 2 is almost independent of the used positioning method Next steps: consider other factors which have an influence on the accuracy of the X-maps UE inaccuracies number of measurements taken consider real measurement data 13/13

14 Thank you! 14/13